1. Field
The present invention relates generally to electromagnetic radiation and reception, and more specifically to ultra wide band antennas for wireless communications.
2. Background
Ultra Wideband (UWB) radio is a wireless technology for transmitting digital data over a wide spectrum of frequency bands with very low power. It can transmit data at very high rates (for wireless local area network applications). Within certain power limits allowed, Ultra Wideband can not only carry huge amounts of data over a short distance at very low power, but also has the ability to carry signals through doors and other obstacles that tend to reflect signals at more limited bandwidths and a higher power. At higher power levels, UWB signals can travel to significantly greater ranges. Instead of traditional sine waves, ultra wideband radio broadcasts digital pulses that are timed very precisely on a signal across a very wide spectrum at the same time. Transmitter and receiver must be coordinated to send and receive pulses with an accuracy of trillionths of a second. Ultra wideband can also be used for very high-resolution radars and precision (sub-centimeter) radio location systems.
Since UWB systems may consume very little power, around one ten-thousandth of that of cell phones, this makes UWB practical for use in smaller devices, such as cell phones and PDAs that users carry at all times. With UWB operating at such low power, it may have very little interference impact on other systems. UWB may cause less interference than conventional radio-network solutions. In addition, the relatively wide spectrum that UWB utilizes can significantly minimize the impact of interference from other systems as well.
A UWB antenna must have a very wide bandwidth such as in the frequency range of approximately 3 GHz to 10 GHz that is nearly omni-directional in the horizon, small in size with low physical profile and that is inexpensive to manufacture and to embed, if necessary, in a wireless communication device.
An antenna that can be considered for use as an UWB antenna is a half-wave antenna, referred to as a dipole, or doublet, which consists of two lengths of wire rod, or tubing, each ¼ wavelength long at a certain frequency. It is the basic unit from which many complex antennas are constructed. The half-wave antenna operates independently of ground; therefore, it may be installed above the surface of the Earth or other absorbing bodies.